1 . Field of the Invention
The present invention relates to a power amplifier of a mobile communications terminal, and particularly, to a power protecting apparatus and method of a power amplifier.
2 . Background of the Related Art
The so-called near-far problem, which related to a reception sensitivity between a mobile communications terminal and a base station, refers to a backward power control procedure and causes a path loss according to the distance between the mobile communications terminal and the base station.
For example, a low transmission power level of the base station increases a bit error rate, while a high transmission power level thereof causes an interface between the mobile communications terminal and the base station, resulting in degraded service quality. The base station must provide services with the same quality to every mobile communications terminal by receiving radio communication signals from the mobile communications terminals using the same power level. Accordingly, the base station uses a Pulse Density Modulation (PDM) signal to control the transmission power of each mobile communications terminal.
In order to control the transmission power, the mobile communications terminals use a gain adjustment method, namely, a two-stage power amplifying method in which the transmission power of the mobile communications terminal can be controlled based upon a high gain mode and a low gain mode. Here, in order to optimize current consumption, a battery power of the high gain mode or a DC/DC converter power of the low gain mode is selected to be used as an operation power of a power amplifier within the mobile communications terminal. The mobile communications terminal can control its transmission power by using the selected power as the operation power of the power amplifier therein.
However, the two-stage power amplifying method repeatedly switches a high level transmission power and a low level transmission power in a high speed manner in order to support the mobility of the mobile communications terminal. Accordingly, it is possible to allow an increase or a decrease of the levels of the transmission power. However, the repeated switching operation at high speed momentarily cuts off the forward voltage that forms across an inductor, and thereby generates an excessive backward voltage. As a result, undesirable hard damage occurring within and impairing the power circuit causes many problems.